A crossarm is a rigid member that is secured to a vertical pole for the purpose of supporting one or more power lines above the ground. Typically, the vertical pole is a wooden pole. The crossarm can be made of many materials, but crossarms made of treated wood have the requisite structural characteristics, are relatively inexpensive, and can last up to 50 years or more when properly installed and maintained. The present invention relates to wood crossarms.
A first portion of a crossarm is typically secured to a first location on the pole by a crossarm bolt that extends through the pole and the crossarm. Many crossarms are also supported at a second portion, and often a third portion, by one or more brace assemblies. The brace assemblies extend between the pole at a second location below the first location and the second and/or third portions of the crossarm. Whether or not brace assemblies are used, the resulting structure is engineered to allow the loads of power lines and the like to be suspended from the crossarm.
As generally discussed above, treated wood has desirable cost and structural properties and, overall, is preferred for use as a crossarm. The term “treated wood” as used herein refers to a wooden member that has been treated with a preservative material. The preservative material typically includes pesticides such as insecticides, fungicides, and the like that discourage the growth of biological organisms that would otherwise degrade the structural properties of wood over time. Typically, the preservative material uses oil or water as a vehicle for carrying the pesticides into the wooden member.
In particular, a wooden member is milled into the desired shape of a crossarm. The surface of the wooden member is then incised to allow for improved penetration of the preservative into the wood. The wooden member is then immersed in the preservative material in a pressure tank. The tank is pressurized to force the preservative material into the wooden member to obtain the treated wood crossarm. Depending on the specie of wood, the preservative material may or may not penetrate completely through the wooden member; the preservative material may only extend into a boundary region that is protected by the preservative material, leaving an interior region that is unprotected by pesticides.
One cause of the premature failure of wooden crossarm members relates to splitting of the ends of the wooden member. In wood crossarms that are not totally penetrated by pesticides, such splitting allows the untreated interior region of the wooden member to be exposed to biological organisms that cause it to degrade. Splitting also adversely affects the ability of a wooden crossarm to bear the loads placed thereon by power lines and the like. In either case, splitting of the crossarm member can result in failure of the crossarm system.
The need thus exists for crossarm systems and methods that are less susceptible to splitting and the system failures associated therewith.